Many Football Players Have Mild, Severe Chronic Traumatic Encephalopathy

Chronic traumatic encephalopathy can only be diagnosed postmortem. Image courtesy Boston University School of Medicine.

A groundbreaking study recently published in JAMA found compelling evidence of a strong link between chronic traumatic encephalopathy (CTE) and North American football. Neuropathological evidence of CTE was identified on autopsy in the brains of 177 of 202 deceased men who had played football at the college level or higher for at least 2 years. Most striking was that 110 of 111 former National Football League players were neuropathologically diagnosed with severe CTE.

A group of investigators from the Neuropathology Service of the Veteran's Affairs Boston Healthcare System and the Boston University Alzheimer's Disease Center examined a convenience sample of 202 brains donated to a collaborative brain bank designed to better understand the long-term effect of repetitive head trauma. All participants in the study were men who died after age 35 years and who had played at least 2 years of college- or higher-level football.

Distribution of CTE showed a relationship between the level of play and the severity of disease, with the mildest CTE seen among 3 former high school players and the most severe cases seen among the 86% of players who were National Football League players and the players in the Canadian Football League. The mean duration of play among participants with mild CTE was 13 years (standard deviation, 4.2 years) compared with 15.8 years (standard deviation, 5.3 years) among those with severe CTE at autopsy.

Neuropathological findings were also associated with an array of behavioral, cognitive, language, and visuospatial symptoms reported in the informant histories of patients with both mild and severe CTE in the years before death. Behavioral symptoms and mood dysfunctions were reported by informants in 43% of cases as the first sign: 26 (96%) participants with mild CTE and 75 (89%) severe CTE cases.

An evolutionary pattern to the disease was also observed, in which decreasing prevalence from mild to severe CTE was reported across several mood and behavioral symptoms, including impulsivity, depression, and anxiety, ranging from 23 (89%), 18 (67%), and 14 (52%) in mild cases to 65 (80%), 46 (56%), and 41 (50%) in severe cases, respectively. Cognitive symptoms appeared to increase with severity, being reported in 85% of mild CTE cases and 95% of severe cases.

Other symptoms of hopelessness, explosivity, and verbally and physically violent tendencies were reported in 69%, 67%, 63%, and 52% of mild CTE cases, respectively. Suicidal behavior (ideation, attempts, or completions) was identified in 56% of mild CTE cases and was the leading cause of death for these participants. This skewed the median age at the time of death to occur at a significantly younger age for patients with mild CTE (44 years; interquartile range, 29-64 years) compared with those with severe CTE (71 years; interquartile range, 64-79 years), who most frequently died from neurodegenerative causes.

This study was the largest CTE case series ever conducted, and the results are likely to have an effect on all sports in which head trauma occurs. In an interview with CNN, senior author Ann McKee, MD, chief of neuropathology at the VA Boston Healthcare System at Boston University, stated, "There's no question that there's a problem in football...and we urgently need to find answers for not just football players, but veterans and other individuals exposed to head trauma."

The investigators were careful to point out a selection bias in which the football players whose brains were donated to the brain bank for study had histories of repeated head trauma and many had significant clinical signs of brain damage at the time of death. The high frequency of CTE among this cohort was expected, and not generalizable to the overall population of football players.